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Fuel requirements based on compression.

2882 Views 6 Replies 5 Participants Last post by  blasterman88
Hi Neil,

I have an 87 250r with a PSI 425 powervalve cylinder on it. I live in northern Alberta, Canada, and we use this set up for 6 hour endurance ice racing. I am having a debate with my riding partner about what type of fuel we should be running for this set up. We have set the dial-a-dome on the head for 165psi and he feels that we need to be running straight race gas. On the psi website, they say that for 175-190psi, you can run premium, for 195-220psi, 50/50 mix, and for 225-250psi, full race gas. The reason we are having this debate is that one of our competitors has been running this set up for a few years and he claims that you have to run straight race gas at 165psi. I'm saying he's spending money on race gas for nothing. What do you think?
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I would say with 165 compression, you could probably use 87 pump gas low as that is. Any time you have compression over 220 you should use race gas. You should figure in things like, where the ignition timming is set, if its advanced alot you need more fuel to keep the piston cool.
Temps outside makes a difference as well. Maybe not as much for you guys because its so cold there, but we have very hot weather around here & just makes the engines run hotter.

One thing about race gas, & this might be the reason that guy is saying to use it, its the best grade you can get, not like the pump gas.
Pump gas, you realy dont know from one tank full to the other if its the same or not. Service stations dont care if you get quality fuel, why should they, you got to buy it from somewhere & your going to pay top price wheather it the best grade or the poorest.
Race gas, those vendors have to have a product thats up to spect or else they wont be selling it for very long.
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